This book deals with prosodic, syntactic, semantic, pragmatic and in particular with functional and textual aspects of cleft and pseudo-cleft constructions, arguing that they have unique communicative values based upon their logico-semantic, thematic and informational properties. Actual examples are drawn from the London-Lund corpus of spoken English and the Lancaster-Oslo-Bergen corpus of written English, which allows to discern constructions that share properties with cleft-constructions, but do not possess their prototypical form.